﻿
CREATE FUNCTION [fnGetDistance](@LatBegin REAL, @LngBegin REAL, @LatEnd REAL, @LngEnd REAL) RETURNS FLOAT
AS
 BEGIN
   --距离(千米) 
   DECLARE @Distance REAL 

   DECLARE @EARTH_RADIUS REAL 

   SET @EARTH_RADIUS = 6378.137   

   DECLARE @RadLatBegin REAL,@RadLatEnd REAL,@RadLatDiff REAL,@RadLngDiff REAL 

   SET @RadLatBegin = @LatBegin *PI()/180.0   

   SET @RadLatEnd = @LatEnd *PI()/180.0   

   SET @RadLatDiff = @RadLatBegin - @RadLatEnd   

   SET @RadLngDiff = @LngBegin *PI()/180.0 - @LngEnd *PI()/180.0

   SET @Distance = 2 *ASIN(SQRT(POWER(SIN(@RadLatDiff/2), 2)+COS(@RadLatBegin)*COS(@RadLatEnd)*POWER(SIN(@RadLngDiff/2), 2))) 

   SET @Distance = @Distance * @EARTH_RADIUS   

   --SET @Distance = Round(@Distance * 10000) / 10000 

   RETURN @Distance 
END 

SELECT * FROM 商家表名 WHERE fnGetDistance(121.4625,31.220937,longitude,latitude) < 5